#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[]) {
    int shm_id;
    char *shm_buf;

    if (argc != 2) {
        printf("USAGE: atshm <identifier>\n");
        exit(1);
    }

    shm_id = atoi(argv[1]);

    if ((shm_buf = shmat(shm_id, 0, 0)) < (char *)0) {
        perror("shmat fail!\n");
        exit(1);
    }

    printf("segment attached at %p\n", shm_buf);
    system("ipcs -m");
    printf("The string in SHM is :%s\n", shm_buf); // 将共享内存区的内容打印出来
    getchar();

    if ((shmdt(shm_buf)) < 0) {
        perror("shmdt");
        exit(1);
    }

    printf("segment detached \n");
    system("ipcs -m");

    getchar();
    exit(0);
}